Method of making lead-in seals



Sept. 18, 1945. 1 c, GQODALE 2,384,833

' -1\4/IETHOD OF MAKING A LEAD-IN SEAL Filed May 27, 1942 Patented Sept. 18, 1945 METHOD OF MAKING LEAD-IN SEALS Lynn 0. Goodale, Newark, N. 1., assignor to Federal Telephone and Radio Corporation, a

corporation of Delaware Application May 27, 1942, Serial No. 444,665

Claims.

It is an object of my invention to seal a metal rod, such as a tungsten electrode supporting rod through a glass envelope without rotating the parts relative'to the heating fire.

In accordance with a feature of my invention a hole or. aperture lsprovided in a glass blank. The rod, previously beaded, is arranged to extend through the hold or aperture with the bead a little below the glass blank. Fire is then applied to the glass blank from the upper side, generally the side which will later form the inside of the tube. This fire is made to contact the glass of the blanksimultaneously all around the edges of' said aperture. to soften the glass of the blank so that it will fall away and seal to the bead on the rod. The fire maybein the form of a single large fiame, or may be provided as a ring of flame about the aperture. PreferabLv, the glass bead is heated slightly during the'sealing process, and after the glass is softened the rod is moved slightly up and down to puddle the glass. and improve the seal.

A better understanding of my invention may be had from the particular description thereof made with reference to the accompanying drawing in which Fig. 1 is a sectional view of parts illustrating apparatus for practising'the method of my invention;

Fig. 21s a completed seal such as that of Fig. 1, and

Fig. 3 is a sectional view showing alternative apparatus for practising the invention.

In Fig. l'is shown a rod iii, preferably of tungsten. On rod i0 is provided a glass bead ii having at one end an invert as indicated at l2. This glass bead may be formed by first beading the glass with a tubular section or sleeve and then winding on soft glass forming it with invert at I! by means of a graphite paddle or the like. The glass end-plate or cup is shown at I! and has a hole il provided therein. This hole may be provided by stamping out the glass in a manner indicated in my copending application Ser. No. 339,- 480, filed June 8, 1940, which issued as Patent No. 2,339,850 on Jan. 25, 1944. Although I! is shown in this instance as being a cup shaped portion, it

is clear that any desired form of glass plate or bulb may be used.

Rod III is inserted centrally through hole It to such a position that the head I! is arranged only slightly below the hole or aperture ll. These elements, of course, are held in place in a suitable Jig, not shown, and the glass is then fired by flame from a burner nozzle shown at |I.- The flame it from I! is preferably quite large so that it extends down 'over the end of rod Ill and plays against the surface of plate It adiacent opening II. This heating of the glass softens the plate all the way around hole ll so that the softened glass tends to fall away and seal to bead It. In order that the seal may be more readily formed, the bead ll may be pre-heated by use of small fires H, which are preferably maintained at a low enough temperature so as not to fuse head I I but merely to bring it to a high temperature.

Preferably while the glass is fused the tungsten rod i2 is. moved baclaand forward slightly so as to puddle the melted glass and thereby form a better seal. r

' II had been completelyfused with bead l I. Also,

because of the movement of rod I. back and forth, the glass also has sealed somewhat to the rod so as to produce the upward extending portion I. of the glass within-the seal.

It is clear that instead of using a single large flame to fire the glass, as shown in Fig. 1. the

glass may be heated by means of small fires extending around the central rod l0. Such an arrangement is illustrated in Fig. 3. In this figure in place of a large burner II a ring burner 2! fed with gas by way of conduit 2! is shown.

Fires from burner 26 serve to heat the glass plate i3 through the openings or hole M in the same manner as did the flame It, of Fig. 1. Also, in this figure a ring burner 21 is shown for pr'e-heating the glass bead instead of individual burners, such as shown in Fig. 1.

It is clear that the seal formed with the arrangement of Fig. 3 will be substantially the same as that formed in the case of Fig. 1.

While for the purposes of simplicity the sealing of only a single rod is shown, it is clear that the principles of my invention apply equally well to the sealing of a plurality of rods through any glass plate. In order to practice the method, when a plurality of rods is used, it is only necessary that the suitable jigs be provided to support all of these rods in apertures in the plate, and

By use of the method disclosed herein, no rotation of the part with respect to the flame is necessary during the sealing period. It is, therefore, clear that in a mass production of tubes, a continuous conveyor system could be worked out wherein the elements intermittently move into position under the firesfor a period suficient to cause fusing of the glass andcompletion or the seal.

It should be distinctlyunderstood that while i have shown specific examples illustrating the methodin accordance with my invention, other arrangements may be readily apparent to those skilled in the art. These examples are given merely by way of illustration and'are not to he considered as defining or limiting the scope of my invention.

What I claim is:

1. The method of sealing a previously beaded rod through anaperture in a glass plate, comprising making an aperture in said glass plate larger thanthe cross section of the rod hut smaller than that of the bead, positioning said rod substantially vertically through said aperture with the top of the glass bead slightly belowand spaced from said aperture, and app ying heat to said plate on the side away from said bead to soften the glass about said aperture so that it will drop onto and seal to said bead.

2. The method according to claim 1, further comprising heating said bead to a temperature below the fusing point while said heat is applied to said plate. I

3. The method of sealing a conductor rod through a'glass plate, which comprises forming a glass bead on said rod, making an aperture through said glass plate larger than the cross section of the rod but smaller than that of said head, positioning said rod substantially vertically through said aperture with the top of the glass bead below and spaced from said aperture, and

Sill

applying heat to the upper side of said plate simultaneously to several marginal portions symmetrically arranged about said aperture to soften the glass about said aperture so that it will drop onto and seal to the top of the said bead.

d. The method of sealing a conductor rod through a glass member which comprises sealing a glass head to the rod, forming through said glass member an aperture larger than the cross section of the rod but smaller than that of the bead, positioning said rod substantially vertically through said aperture with the top of the glam bead slightly below and spaced from the marginal region of said aperture facing the top oi the bead, applying heat to said member along the circumference of said aperture to soften the glass so that it will descend into contact with the bead, and continuing said application of heat to fuse said marginal region and the top of the bead together to form a seal.

5. A method of sealing a previously glass-bead ed rod through a. glass plate comprising making an aperture in said plate smaller than the cross section of the glass bead but larger than that of the rod, positioning said rod substantially vertically through said aperture with the top oi the glass bead slightly below. said aperture, applying heat to said plate on the side away from said bead to soften the glass about said aperture so that it will drop onto and seal to said head, and moving said rod up and down relative to said glass plate while the glass plate is molten to puddle said glass.

' L C. GOODAKE. 

